This invention relates to a method for the manufacture of an electrode excelling in corrosion-resisting property and having a porous ceramic substrate coated with electrodeposited lead dioxide and to the electrode manufactured by said method. There are the following three types of lead dioxide electrodes known to the art:
A. The type of electrodes produced by having lead dioxide anodically deposited on the surface of a lead substrate.
B. The type of electrodes formed solely of lead dioxide without using any substrate.
C. The type of electrodes produced by having lead dioxide electrodeposited on the substrate of a corrosion-resisting substance other than lead.
Of these three types, those of types b and c are called electrodeposited lead dioxide electrodes and they excel over those of type a in terms of corrosion-resisting property. They have already been put to practical use as electrodes convenient for the electrolysis of aqueous solutions.
The electrodeposited lead dioxide electrodes generally available on the market include rectangular lead dioxide electrodes devoid of a substrate and lead dioxide electrodes possessed of a substrate of graphite, titanium or tantalum or a substrate of such metal having the surface thereof plated with platinum, gold or silver. At the present, lead dioxide electrodes using a titanium substrate are enjoying favorable acceptance in the market.
The electrodeposited lead dioxide electrodes described above have their demerits: For example, the type of lead dioxide electrodes using no substrate are susceptible to fracture and therefore have their shape and dimensions inevitably limited and the type of electrodes using a graphite, titanium or tantulum substrate easily sustain cracks. When a crack occurs in such an electrode in the course of an electrolytic reaction, the solution undergoing the electrolysis penetrates through the crack and eventually comes into contact with the underlying substrate, with the result that the substrate is corroded by the solution. The crack, therefore, has an adverse effect on the service life of the electrode.
A primary object of the present invention is to provide a method for the manufacture of an electrodeposited lead dioxide electrode which incorporates a substrate of high corrosion-resisting property and therefore permits desired electrolysis to be performed without entailing troubles for a long time.
Another object of the present invention is to provide electrodeposited lead dioxide electrodes which enjoy high resistance to corrosion and withstand use conditions for a long time.